This invention relates to a solar collector of the curved type, having a relatively simple structure. The present invention relates more particularly to solar collectors of spherical or semispherical shape of simplified structure.
The solar collectors belong to the type of those comprising two concentric semispheres or spheres, the outer sphere or semisphere being translucent and the inner sphere or semisphere being absorbent of the solar radiation, as well as inlet and outlet ducts for the fluid to be heated.
The use of such collectors has already been envisaged for the production of hot water by virtue of the "greenhouse effect", the spherical or hemispherical shapes allowing producing hot water with an efficiency which is not substantially changed by the direction and angle of incidence of the solar rays. In such collectors it is advisable to foresee a circulation of the fluid to be heated such that the fluid is heated up when in contact with the wall of the absorbent inner hemisphere or sphere. The arrangements presently known foresee in this regard to have the fluid to be heated flow through a number of ducts and in the inner chambers of the collector, notably chambers bounded by two spherical, hemispherical or semispherical concentric walls. The result is that the production of such spherical or semispherical solar collectors is at present still relatively complex and costly.
It is known from U.S. Pat. No. 4,056,093 to provide a solar energy unit with an upwardly facing opening generally hemispherical double wall boiler including spaced inner and outer hemispherical walls defining a closed chamber therebetween in which to receive a liquid to be heated. An upwardly convex spherical lens structure is supported over the boiler and comprises a closure for the area enclosed within the boundaries of the inner hemispherical wall of the boiler and the lens assembly or structure functions to direct light rays incident thereon onto the inner wall of the boiler. The solar heater additionally includes a hollow downwardly opening transparent hemispherical cover of generally the same radius of curvature as the boiler and which is secured over the lens assembly in outwardly spaced position relative thereto with the center of curvature of the cover substantially coinciding with the center of curvature of the lens assembly.
It is known from U.S. Pat. No. 4,136,670 to provide a solar heating system including an energy absorbent collector dish for receiving solar heat, a supply tube for distributing a heat transfer fluid over the collector dish, a drain pipe for removing the heat transfer liquid from the collector dish and an optical director including an array of converging lenses oriented to receive radiant energy from the sun and to direct the energy onto the collector dish. The array of converging lenses comprises a matrix of double convex lenses that form one half of a hemispherical optical dome, the other half of which possesses an inner reflective surface for reflecting radiant energy onto the collector dish and the optical dome is oriented such that some portion of the lens array faces the sun during an entire day's movement.